Answer should be 1.5 !!!

Let the trees be x,y

from question : -

eq1 is x = 3/5 (y)

eq2 after 4 yrs,

x+y = 8

from the 2 equations we get y = 5 and x = 3

according to our equation x= 3/5(y) -> x is the smaller tree.

In 4 yrs x grows 3ft

In 2 yrs x grows ?ft

Ans = 1.5ft.